debug.h File Reference

#include "lib/alignment.h"
#include "lib/code_annotation.h"
#include "lib/code_generation.h"
#include "lib/status.h"
#include "lib/types.h"

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Namespaces
	ERR
	Introduction
	INFO

Macros
#define	DEBUG_DISPLAY_ERROR_IMPL(description, flags)
#define	DEBUG_DISPLAY_ERROR(description)   DEBUG_DISPLAY_ERROR_IMPL(description, 0)
#define	DEBUG_DISPLAY_FATAL_ERROR(description)   DEBUG_DISPLAY_ERROR_IMPL(description, DE_NO_CONTINUE)
#define	ENSURE(expr)
	ensure the expression <expr> evaluates to non-zero. More...
#define	ASSERT(expr)   ENSURE(expr)
	same as ENSURE in debug mode, does nothing in release mode. More...
#define	debug_warn(expr)   ENSURE(0 && (expr))
	display the error dialog with the given text. More...
#define	DEBUG_WARN_ERR(status)
	display the error dialog with text corresponding to the given error code. More...

Typedefs
typedef volatile intptr_t	atomic_bool
	a bool that is reasonably certain to be set atomically. More...

Enumerations
enum	DebugDisplayErrorFlags { DE_NO_CONTINUE = 1, DE_ALLOW_SUPPRESS = 2, DE_MANUAL_BREAK = 4, DE_NO_DEBUG_INFO = 8 }
	flags to customize debug_DisplayError behavior More...
enum	ErrorReaction { ER_CONTINUE = 1, ER_BREAK }
	choices offered by the error dialog that are returned by debug_DisplayError. More...
enum	ErrorReactionInternal {   ERI_CONTINUE = ER_CONTINUE, ERI_BREAK = ER_BREAK, ERI_SUPPRESS, ERI_EXIT,   ERI_NOT_IMPLEMENTED }
	all choices offered by the error dialog. More...

Functions
void	debug_break ()
	trigger a breakpoint when reached/"called". More...
void	debug_printf (const char *fmt,...) PRINTF_ARGS(1)
	write a formatted string to the debug channel, subject to filtering (see below). More...
void	debug_DisplayMessage (const wchar_t *caption, const wchar_t *msg)
	translates and displays the given strings in a dialog. More...
ErrorReaction	debug_DisplayError (const wchar_t *description, size_t flags, void *context, const wchar_t *lastFuncToSkip, const wchar_t *file, int line, const char *func, atomic_bool *suppress)
	display an error dialog with a message and stack trace. More...
void	debug_filter_add (const char *tag)
	debug output is very useful, but "too much of a good thing can kill you". More...
void	debug_filter_remove (const char *tag)
	in future, discard output with the given tag. More...
void	debug_filter_clear ()
	clear all filter state; equivalent to debug_filter_remove for each tag that was debug_filter_add-ed. More...
bool	debug_filter_allows (const char *text)
	indicate if the given text would be printed. More...
void	debug_puts_filtered (const char *text)
	call debug_puts if debug_filter_allows allows the string. More...
Status	debug_WriteCrashlog (const char *text)
	write an error description and all logs into crashlog.txt (in unicode format). More...
ErrorReaction	debug_OnAssertionFailure (const wchar_t *assert_expr, atomic_bool *suppress, const wchar_t *file, int line, const char *func) ANALYZER_NORETURN
	called when a ENSURE/ASSERT fails; notifies the user via debug_DisplayError. More...
ErrorReaction	debug_OnError (Status err, atomic_bool *suppress, const wchar_t *file, int line, const char *func) ANALYZER_NORETURN
	called when a DEBUG_WARN_ERR indicates an error occurred; notifies the user via debug_DisplayError. More...
void	debug_SkipErrors (Status err)
	suppress (prevent from showing) the error dialog from subsequent debug_OnError for the given Status. More...
size_t	debug_StopSkippingErrors ()
Status	debug_ResolveSymbol (void *ptr_of_interest, wchar_t *sym_name, wchar_t *file, int *line)
	read and return symbol information for the given address. More...
Status	debug_CaptureContext (void *context)
Status	debug_DumpStack (wchar_t *buf, size_t maxChars, void *context, const wchar_t *lastFuncToSkip)
	write a complete stack trace (including values of local variables) into the specified buffer. More...
void	debug_puts (const char *text)
	[system-dependent] write a string to the debug channel. More...
void *	debug_GetCaller (void *context, const wchar_t *lastFuncToSkip)
	return the caller of a certain function on the call stack. More...
int	debug_IsPointerBogus (const void *p)
	check if a pointer appears to be totally invalid. More...
bool	debug_IsCodePointer (void *p)
	does the given pointer appear to point to code? More...
bool	debug_IsStackPointer (void *p)
	does the given pointer appear to point to the stack? More...
void	debug_SetThreadName (const char *name)
	inform the debugger of the current thread's name. More...
const wchar_t *	debug_BuildErrorMessage (const wchar_t *description, const wchar_t *fn_only, int line, const char *func, void *context, const wchar_t *lastFuncToSkip)
	build a string describing the given error. More...

Variables
static const atomic_bool	DEBUG_SUPPRESS = 0xAB
	value for suppress flag once set by debug_DisplayError. More...
const Status	ERR::SYM_NO_STACK_FRAMES_FOUND = -100400
const Status	ERR::SYM_UNRETRIEVABLE_STATIC = -100401
const Status	ERR::SYM_UNRETRIEVABLE = -100402
const Status	ERR::SYM_TYPE_INFO_UNAVAILABLE = -100403
const Status	ERR::SYM_INTERNAL_ERROR = -100404
const Status	ERR::SYM_UNSUPPORTED = -100405
const Status	ERR::SYM_CHILD_NOT_FOUND = -100406
const Status	ERR::SYM_NESTING_LIMIT = -100407
const Status	ERR::SYM_SINGLE_SYMBOL_LIMIT = -100408
const Status	INFO::SYM_SUPPRESS_OUTPUT = +100409
static const size_t	DEBUG_SYMBOL_CHARS = 1000
	Maximum number of characters (including null terminator) written to user's buffers by debug_ResolveSymbol. More...
static const size_t	DEBUG_FILE_CHARS = 100
static const size_t	DEBUG_CONTEXT_SIZE = 2048

Macro Definition Documentation

ASSERT

#define ASSERT

(

expr

)

ENSURE(expr)

same as ENSURE in debug mode, does nothing in release mode.

(we don't override the `assert' macro because users may inadvertently include <assert.h> afterwards) (we do not provide an MFC-style VERIFY macro because the distinction between ENSURE and VERIFY is unclear. to always run code but only check for success in debug builds without raising unused-variable warnings, use ASSERT + UNUSED2.)

DEBUG_DISPLAY_ERROR

#define DEBUG_DISPLAY_ERROR

(

description

)

DEBUG_DISPLAY_ERROR_IMPL(description, 0)

DEBUG_DISPLAY_ERROR_IMPL

#define DEBUG_DISPLAY_ERROR_IMPL	(		description,
			flags
	)

Value:

do\
    {\
        CACHE_ALIGNED(u8) context[DEBUG_CONTEXT_SIZE];\
        (void)debug_CaptureContext(context);\
        (void)debug_DisplayError(description, flags, context, L"debug_DisplayError", WIDEN(__FILE__), __LINE__, __func__, 0);\
    }\
    while(0)

DEBUG_DISPLAY_FATAL_ERROR

#define DEBUG_DISPLAY_FATAL_ERROR

(

description

)

DEBUG_DISPLAY_ERROR_IMPL(description, DE_NO_CONTINUE)

debug_warn

#define debug_warn

(

expr

)

ENSURE(0 && (expr))

display the error dialog with the given text.

this is less error-prone than ENSURE(0 && "text"). note that "conditional expression is constant" warnings are disabled anyway.

if being able to suppress the warning is desirable (e.g. for self-tests), then use DEBUG_WARN_ERR instead.

DEBUG_WARN_ERR

#define DEBUG_WARN_ERR

(

status

)

Value:

do\
    {\
        static atomic_bool suppress__;\
        switch(debug_OnError(status, &suppress__, WIDEN(__FILE__), __LINE__, __func__))\
        {\
        case ER_CONTINUE:\
            break;\
        case ER_BREAK:\
        default:\
            debug_break();\
            break;\
        }\
    }\
    while(0)

display the error dialog with text corresponding to the given error code.

used by WARN_RETURN_STATUS_IF_ERR et al., which wrap function calls and automatically raise warnings and return to the caller.

ENSURE

#define ENSURE

(

expr

)

Value:

do\
    {\
        static atomic_bool suppress__;\
        if(!(expr))\
        {\
            switch(debug_OnAssertionFailure(WIDEN(#expr), &suppress__, WIDEN(__FILE__), __LINE__, __func__))\
            {\
            case ER_CONTINUE:\
                break;\
            case ER_BREAK:\
            default:\
                debug_break();\
                break;\
            }\
        }\
    }\
    while(0)

ensure the expression <expr> evaluates to non-zero.

used to validate invariants in the program during development and thus gives a very helpful warning if something isn't going as expected. sprinkle these liberally throughout your code!

to pass more information to users at runtime, you can write ENSURE(expression && "descriptive string").

Typedef Documentation

atomic_bool

typedef volatile intptr_t atomic_bool

a bool that is reasonably certain to be set atomically.

we cannot assume support for OpenMP (requires GCC 4.2) or C++0x, so we'll have to resort to intptr_t, cpu_CAS and COMPILER_FENCE.

Enumeration Type Documentation

DebugDisplayErrorFlags

enum DebugDisplayErrorFlags

flags to customize debug_DisplayError behavior

Enumerator
DE_NO_CONTINUE	disallow the Continue button. used e.g. if an exception is fatal.
DE_ALLOW_SUPPRESS	enable the Suppress button. set automatically by debug_DisplayError if it receives a non-NULL suppress pointer. a flag is necessary because the sys_display_error interface doesn't get that pointer. rationale for automatic setting: this may prevent someone from forgetting to specify it, and disabling Suppress despite having passed a non-NULL pointer doesn't make much sense.
DE_MANUAL_BREAK	do not trigger a breakpoint inside debug_DisplayError; caller will take care of this if ER_BREAK is returned. this is so that the debugger can jump directly into the offending function.
DE_NO_DEBUG_INFO	display just the given message; do not add any information about the call stack, do not write crashlogs, etc.

ErrorReaction

enum ErrorReaction

choices offered by the error dialog that are returned by debug_DisplayError.

Enumerator
ER_CONTINUE	ignore, continue as if nothing happened. note: value doesn't start at 0 because that is interpreted as a DialogBoxParam failure.
ER_BREAK	trigger breakpoint, i.e. enter debugger. only returned if DE_MANUAL_BREAK was passed; otherwise, debug_DisplayError will trigger a breakpoint itself.

ErrorReactionInternal

enum ErrorReactionInternal

all choices offered by the error dialog.

those not defined in ErrorReaction are acted upon by debug_DisplayError and never returned to callers. (this separation avoids enumerator-not-handled warnings)

Enumerator
ERI_CONTINUE
ERI_BREAK
ERI_SUPPRESS	ignore and do not report again. note: non-persistent; only applicable during this program run.
ERI_EXIT	exit the program immediately.
ERI_NOT_IMPLEMENTED	special return value for the display_error app hook stub to indicate that it has done nothing and that the normal sys_display_error implementation should be called instead.

Function Documentation

debug_break()

void debug_break

(

)

trigger a breakpoint when reached/"called".

if defined as a macro, the debugger can break directly into the target function instead of one frame below it as with a conventional call-based implementation.

debug_BuildErrorMessage()

const wchar_t* debug_BuildErrorMessage	(	const wchar_t *	description,
		const wchar_t *	fn_only,
		int	line,
		const char *	func,
		void *	context,
		const wchar_t *	lastFuncToSkip
	)

build a string describing the given error.

this is a helper function used by debug_DumpStack and is made available so that the self-test doesn't have to display the error dialog.

Parameters

description	general description of the problem.
fn_only	filename (no path) of source file that triggered the error.
line,func	exact position of the error.
context,lastFuncToSkip	see debug_DumpStack.

debug_CaptureContext()

Status debug_CaptureContext

(

void *

context

)

Parameters

context

must point to an instance of the platform-specific type (e.g. CONTEXT) or CACHE_ALIGNED storage of DEBUG_CONTEXT_SIZE bytes.

debug_DisplayError()

ErrorReaction debug_DisplayError	(	const wchar_t *	description,
		size_t	flags,
		void *	context,
		const wchar_t *	lastFuncToSkip,
		const wchar_t *	file,
		int	line,
		const char *	func,
		atomic_bool *	suppress
	)

display an error dialog with a message and stack trace.

Parameters

description	text to show.
flags	see DebugDisplayErrorFlags.
context,lastFuncToSkip	see debug_DumpStack.
file,line,func	location of the error (typically passed as WIDEN(FILE), LINE, func from a macro)
suppress	pointer to a caller-allocated flag that can be used to suppress this error. if NULL, this functionality is skipped and the "Suppress" dialog button will be disabled. note: this flag is read and written exclusively here; caller only provides the storage. values: see DEBUG_SUPPRESS above.

Returns

ErrorReaction (user's choice: continue running or stop?)

debug_DisplayMessage()

void debug_DisplayMessage	(	const wchar_t *	caption,
		const wchar_t *	msg
	)

translates and displays the given strings in a dialog.

this is typically only used when debug_DisplayError has failed or is unavailable because that function is much more capable. implemented via sys_display_msg; see documentation there.

debug_DumpStack()

Status debug_DumpStack	(	wchar_t *	buf,
		size_t	maxChars,
		void *	context,
		const wchar_t *	lastFuncToSkip
	)

write a complete stack trace (including values of local variables) into the specified buffer.

Parameters

buf	Target buffer.
maxChars	Max chars of buffer (should be several thousand).
context	Platform-specific representation of execution state (e.g. Win32 CONTEXT). either specify an SEH exception's context record or use debug_CaptureContext to retrieve the current state. Rationale: intermediates such as debug_DisplayError change the context, so it should be captured as soon as possible.
lastFuncToSkip	Is used for omitting error-reporting functions like debug_OnAssertionFailure from the stack trace. It is either 0 (skip nothing) or a substring of a function's name (this allows platform-independent matching of stdcall-decorated names). Rationale: this is safer than specifying a fixed number of frames, which can be incorrect due to inlining.

Returns

Status; ERR::REENTERED if reentered via recursion or multithreading (not allowed since static data is used).

debug_filter_add()

void debug_filter_add

(

const char *

tag

)

debug output is very useful, but "too much of a good thing can kill you".

we don't want to require different LOGn() macros that are enabled depending on "debug level", because changing that entails lengthy compiles and it's too coarse-grained. instead, we require all strings to start with "tag_string|" (exact case and no quotes; the alphanumeric-only <tag_string> identifies output type). they are then subject to filtering: only if the tag has been "added" via debug_filter_add is the appendant string displayed.

this approach is easiest to implement and is fine because we control all logging code. LIMODS falls from consideration since it's not portable and too complex.

notes:

• filter changes only affect subsequent debug_*printf calls; output that didn't pass the filter is permanently discarded.
• strings not starting with a tag are always displayed.
• debug_filter_* can be called at any time and from the debugger, but are not reentrant.

in future, allow output with the given tag to proceed. no effect if already added.

debug_filter_allows()

bool debug_filter_allows

(

const char *

text

)

indicate if the given text would be printed.

useful for a series of debug_printfs - avoids needing to add a tag to each of their format strings.

debug_filter_clear()

void debug_filter_clear

(

)

clear all filter state; equivalent to debug_filter_remove for each tag that was debug_filter_add-ed.

debug_filter_remove()

void debug_filter_remove

(

const char *

tag

)

in future, discard output with the given tag.

no effect if not currently added.

debug_GetCaller()

void* debug_GetCaller	(	void *	context,
		const wchar_t *	lastFuncToSkip
	)

return the caller of a certain function on the call stack.

this function is useful for recording (partial) stack traces for memory allocation tracking, etc.

Parameters

context,lastFuncToSkip

- see debug_DumpStack

Returns

address of the caller

debug_IsCodePointer()

bool debug_IsCodePointer

(

void *

p

)

does the given pointer appear to point to code?

debug_IsPointerBogus()

int debug_IsPointerBogus

(

const void *

p

)

check if a pointer appears to be totally invalid.

this check is not authoritative (the pointer may be "valid" but incorrect) but can be used to filter out obviously wrong values in a portable manner.

Parameters

p

pointer

Returns

1 if totally bogus, otherwise 0.

debug_IsStackPointer()

bool debug_IsStackPointer

(

void *

p

)

does the given pointer appear to point to the stack?

debug_OnAssertionFailure()

ErrorReaction debug_OnAssertionFailure	(	const wchar_t *	assert_expr,
		atomic_bool *	suppress,
		const wchar_t *	file,
		int	line,
		const char *	func
	)

called when a ENSURE/ASSERT fails; notifies the user via debug_DisplayError.

Parameters

assert_expr	the expression that failed; typically passed as #expr in the assert macro.
suppress	see debug_DisplayError.
file,line	source file name and line number of the spot that failed
func	name of the function containing it

Returns

ErrorReaction (user's choice: continue running or stop?)

debug_OnError()

ErrorReaction debug_OnError	(	Status	err,
		atomic_bool *	suppress,
		const wchar_t *	file,
		int	line,
		const char *	func
	)

called when a DEBUG_WARN_ERR indicates an error occurred; notifies the user via debug_DisplayError.

Parameters

err	Status value indicating the error that occurred
suppress	see debug_DisplayError.
file,line	source file name and line number of the spot that failed
func	name of the function containing it

Returns

ErrorReaction (user's choice: continue running or stop?)

debug_printf()

void debug_printf	(	const char *	fmt,
			...
	)

write a formatted string to the debug channel, subject to filtering (see below).

implemented via debug_puts - see performance note there.

Parameters

fmt	Format string and varargs; see printf.

debug_puts()

void debug_puts

(

const char *

text

)

[system-dependent] write a string to the debug channel.

this can be quite slow (~1 ms)! On Windows, it uses OutputDebugString (entails context switch), otherwise stdout+fflush (waits for IO).

debug_puts_filtered()

void debug_puts_filtered

(

const char *

text

)

call debug_puts if debug_filter_allows allows the string.

debug_ResolveSymbol()

Status debug_ResolveSymbol	(	void *	ptr_of_interest,
		wchar_t *	sym_name,
		wchar_t *	file,
		int *	line
	)

read and return symbol information for the given address.

NOTE: the PDB implementation is rather slow (~500 us).

Parameters

ptr_of_interest	address of symbol (e.g. function, variable)
sym_name	optional out; holds at least DEBUG_SYMBOL_CHARS; receives symbol name returned via debug info.
file	optional out; holds at least DEBUG_FILE_CHARS; receives base name only (no path; see rationale in wdbg_sym) of source file containing the symbol.
line	optional out; receives source file line number of symbol.

note: all of the output parameters are optional; we pass back as much information as is available and desired.

Returns

Status; INFO::OK iff any information was successfully retrieved and stored.

debug_SetThreadName()

void debug_SetThreadName

(

const char *

name

)

inform the debugger of the current thread's name.

(threads are easier to keep apart when they are identified by name rather than TID.)

debug_SkipErrors()

void debug_SkipErrors

(

Status

err

)

suppress (prevent from showing) the error dialog from subsequent debug_OnError for the given Status.

rationale: for edge cases in some functions, warnings are raised in addition to returning an error code. self-tests deliberately trigger these cases and check for the latter but shouldn't cause the former. we therefore need to squelch them.

Parameters

err	the Status to skip.

note: only one concurrent skip request is allowed; call debug_StopSkippingErrors before the next debug_SkipErrors.

debug_StopSkippingErrors()

size_t debug_StopSkippingErrors

(

)

Returns

how many errors were skipped since the call to debug_SkipErrors()

debug_WriteCrashlog()

Status debug_WriteCrashlog

(

const char *

text

)

write an error description and all logs into crashlog.txt (in unicode format).

Parameters

text	description of the error (including stack trace); typically generated by debug_BuildErrorMessage.

Returns

Status; ERR::REENTERED if reentered via recursion or multithreading (not allowed since an infinite loop may result).

Variable Documentation

DEBUG_CONTEXT_SIZE

const size_t DEBUG_CONTEXT_SIZE = 2048

static

DEBUG_FILE_CHARS

const size_t DEBUG_FILE_CHARS = 100

static

DEBUG_SUPPRESS

const atomic_bool DEBUG_SUPPRESS = 0xAB

static

value for suppress flag once set by debug_DisplayError.

rationale: this value is fairly distinctive and helps when debugging the symbol engine. use 0 as the initial value to avoid allocating .rdata space.

DEBUG_SYMBOL_CHARS

const size_t DEBUG_SYMBOL_CHARS = 1000

static

Maximum number of characters (including null terminator) written to user's buffers by debug_ResolveSymbol.